Adhesives for Needle Bonding
Needles are used throughout healthcare for injection, blood drawing, biopsy, etc… Other industries use needles for dispensing, test fluid extraction and injection, etc… Understanding the use of the needle supports a good understanding of the optimal test methods (eg. Straight needle pull or 90 degree twist) and chemical resistance requirements. Many industrial needles have prolonged exposure to harsh chemicals making epoxy adhesive preferable to light cure adhesives for needle bonding. In other applications the placement of the needle bonding adhesive is critical and in-line QC testing with fluorescent indicators makes light cure adhesive the ideal choice.
The cannula gauge, length of the well, length of engagement with the hub all contribute to the total bond area. In some needle bonding applications a structural bond is formed between the cannula and the hub. In other cases the bond is very strong to the hub and simply locked into the hub by annular rings and other design features.
Design & Viscosity
The appropriate viscosity will quickly fill and level out in the well, in some designs it is desirable for the adhesive to also fill the area beyond the well to utilize the full engagement with the cannula. Care must be taken in understanding the end of the hub. In designs in which the cannula is fully seated or designs in which the cannula extends past the hub engagement area there is little opportunity for the adhesive to wick into the cannula and occlude it. In designs that
Process & Adhesive Chemistry Selection
Single component epoxy adhesives and light cure adhesives are the primary chemistries used. Single component epoxy adhesives provide tough, environmentally resistant strong bonds to metals and eliminate concerns related to depth of cure. Light cure adhesives are often preferred for ease of process, clarity and in needle bonding applications that require a penetrative viscosity to wick between close fitting components.
For further help with needle bonding and adhesive selection, please contact Permabond here.